The Language of HVAC is Tough

August 28, 2006
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English has got to be one of the most difficult languages to master, I mean really - A–E–I–O-U and sometimes Y? Then there are all those synonyms and homonyms. What about all those crazy jingles to help you remember spelling rules: "i before e except after c"? It's enough to make a third grader want to throw up her hands and quit.

And, if that weren't enough, let's say the kid wants to get a job in some promising industry. Think of all the abbreviations and acronyms awaiting her. Communication isn't easy.

For example, take our own industry. Imagine a salesperson walking up to the door of any homeowner (much less an owner who is fresh off the boat): "Hello, I'm the HVAC salesman from A-OK Heating & Cooling. Our tech tells me that your a/c unit is on its last leg and that you're in need of a new IAQ system. May I come in?

"First, I'll measure the Btu loss and gain of your home. That will help you determine which type of unit to buy. We'll go over the various SEER, HSPF, and COP efficiency ratings. And, if you'd like to consider an entire system replacement, we can discuss our highest AFUE furnaces. Then, I'll review our variety of MERV-rated HEPA filtration products, and CADR-rated air cleaning products. We have ..."


"HSPF? Oh, that's just in case you want to buy a heat pump instead of an air conditioner ...

Well, the SEER is related to the EER and also to the COP commonly used in thermodynamics ...

Sure, you could say they're cousins. The EER is the efficiency rating for the equipment at a particular pair of external and internal temperatures, while SEER is calculated over a whole range of external temperatures that more accurately represents the geographic location ...

No, it's not like a policeman. COP is ... well, you see the energy-efficiency ratings measure the amount of electricity required by an air conditioning unit to provide the desired cooling level in Btus. The higher an EER, the more energy efficient a unit is ...

Oh, yeah. Btu is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit ...

That stands for British Thermal Unit ...

Uh, no, they don't actually use Btu measurements very much in the United Kingdom. It's mostly an American thing ...

Well, no Fahrenheit was invented by a German guy, but Jamaica and the United States are just about the only countries now using the measurement ...

Maybe we should talk about the IAQ products that your house might need? Oh, sure. I'd be happy to answer your questions about IAQ. (Cringe.)


No, Merv Griffin doesn't rate the products. MERV stands for minimum efficiency reporting value. A typical MERV rating tells you the arrestance rating of the filter at three particle sizes of 0.3 to 10 microns at a certain face velocity. For example, a rating of MERV 15 corresponds to 85-95 percent arrestance efficiency for particles 0.3 to 1.0 microns, above 90 percent efficiency for particles 1 to 3 microns, and above 90 percent efficiency for particles 3 to 10 microns ...

No, the COP won't arrest you. Arrestance efficiency is based on particle counts taken upstream and downstream of a test filter with an optical, or laser, particle counter - but, we probably don't want to go there ...

Yes, HEPA stands for high-efficiency particulate air. If you want the very best, a HEPA filter will remove 99.97 percent of all airborne pollutants 0.3 microns or larger ...

Oh, the CADR. That's the clean air delivery rate. The Association of Home Appliance Manufacturers (AHAM) designated this measurement as part of an evaluation of portable household electric room air cleaners. We have some of those products available. We also have some whole-house air cleaners ...

Oh, you've heard of CADRs before? ...

I know it's kind of confusing. The terms CADR and Clean Air Delivery Rate are general terms used to make performance claims for many types of products other than portable room air cleaners. CADR values for other products may not have been calculated in accordance with the AHAM definition of CADR. If not, the comparisons between products may not be accurate according to AHAM ...

You're right. Maybe we should do this another time."


As complicated as the English language is, it is the most widely taught and understood in the world. However, "If the English language made any sense, a catastrophe would be an apostrophe with fur," said humorist Doug Larson.

If the HVAC industry's language made any sense, perhaps there wouldn't be as many questions. However, one last acronym for the road: KISS.

Publication date: 08/28/2006

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